Not a Lone Shark: Bulldog Sharks Can Form ‘Friendships’ With Each Other, Study Finds | the Sharks
They grow to 3.5 meters in length, weigh over 200 kg, and are a top predator. But even top predators need friends. And, according to new research, Bulldog Sharks may be able to make some.
A study recently published in Fiji shows that bulldog sharks develop companionship – some sharks showing preferences for some individuals and avoiding others.
Researchers studied data collected from more than 3,000 shark dives at Shark Reef Marine Reserve (SRMR) in Fiji, one of the world’s most sought-after diving destinations. The dives lasted 13 years and noted the behavior of 91 individual Bulldog Sharks, clearly identifiable by external features, such as scars and misshapen or missing fins.
Using a number of statistical approaches, the researchers looked for patterns of associations between sharks that could be explained by factors other than pure chance. And indeed, scientists have found unequivocal evidence of long-term associations.
“Some bulldog shark individuals seem to prefer long-term companions and avoid others,” said Dr. Juerg Brunnschweiler, an independent shark researcher from Switzerland who designed the study.
“Working on the large Fiji dataset was really exciting and scientifically important as there is a large research gap regarding the social behavior of bulldog sharks,” said Dr Thibaut Bouveroux, post-doctoral researcher at Dauphin Island Sea Lab at United States and lead author of the study.
Bouveroux generally studies how and why marine mammals create social bonds. For this study, he used his social structure analysis skills and applied them to Fijian Bulldog Sharks.
“The long-term data collection available has given us a real opportunity to better understand whether Bulldog Sharks are able to develop social links in a stocked site and how they have been affected over time,” he said. declared.
The marine protected area off the coast of Fiji’s largest island, Viti Levu, is home to eight sharks and hundreds of species of fish. Bulldog sharks, large curious animals that can reach up to 3.5 meters in length, are one of the main attractions.
Data from 3,000 shark dives were recorded by Beqa Adventure Divers, a conservation-focused dive center operating on the South Pacific Island since 2003.
“Beqa Adventure Divers has maintained a database that contains data on all shark species, behavioral data and many other parameters from each dive. It’s a rich source of all kinds of information, ”Brunnschweiler said.
However, the fact that the data was collected on ‘baited’ dives – where dive companies place food in the ocean to attract sharks to the dive site – should be taken into account when analyzing the dive sites. results, the researchers warned.
“Presence of the bulldog shark at SRMR [Fiji’s Shark Reef Marine Reserve] is driven by spatial aggregation caused by diet, so we need to be very careful when interpreting our results, ”Brunnschweiler said.
It is not known if sharks show up together because they ‘love each other’, if they simply live nearby, or if they share character traits, such as boldness and curiosity, that drive them. to the stocked site, is not clear.
“The main caveat is that we don’t have a monitoring site,” Brunnschweiler said. “For example, if we have two individuals that are observed together at SRMR more or less regularly, and if they also present together at another site with the same or similar probability as in SRMR, then that would make our results much more robust. And would indicate that there is indeed a certain level of sociality in this species.
But Brunnschweiler said the study provided a solid starting point for future work. He plans to develop this knowledge with additional analysis.
“Future studies will need to identify the personality traits of each shark, determine how particular traits might influence group formation, construct a bull shark hierarchy to determine ranking positions, and then examine the stability of rankings over time. “
Both researchers cautioned against overinterpreting their data.
“Bulldog sharks cannot be considered a social species like marine mammals or other land species like elephants or chimpanzees. However, it appears that some individuals are able to develop preferred co-occurrences or affinities (and avoidances) with certain individuals, ”said Bouveroux.
And while Bulldog Sharks form companions, Brunnschweiler does not approve of the use of the term “friendships” in relation to sharks.
“Friendship is a relationship of mutual affection between people. Not animals, ”he said. “It would be anthropomorphic to talk about friendships here.”